Keeping an upright posture, step forward with one foot, flexing the front knee 90 degrees into a lunge position. Keep your thigh parallel to the floor, and make sure your knee bends no more than 90 degrees.

Tennis strokes start from the ground up: The forces generated by pushing off against the ground can then be transferred to the rest of the body (remember Newton’s third law of motion: To every action there is an equal and opposite reaction). Having strong legs not only helps to enhance your performance, but it also helps prevent injuries.

The lunge is a "multi-joint exercise." As the name indicates, more than one joint is involved (ankles, knees and hips). The key is to train the musculature surrounding these joints. The lunge also mimics positions that occur regularly in tennis matches. Hitting a wide groundstroke or low volley requires the same muscle groups that are trained by performing lunges.

2. Keeping an upright posture, step forward with one foot, flexing the front knee 90 degrees into a lunge position. Keep your thigh parallel to the floor, and make sure your knee bends no more than 90 degrees.

3. Immediately push off the front foot and return to the starting position. Repeat, stepping forward with the other foot. Alternate right and left.

Popover Variations:

45-Degree Lunge:

Instead of stepping directly forward, step outward at a 45-degree angle. This is a great exercise for working muscles needed at the net.

Crossover Lunge:

Cross one foot over the other at a 45-degree angle. This will help stabilize muscles used for closed-stance groundstrokes.

Lateral Lunge:

Works the muscles used to hit wide shots. Rest the dumbbells (if using) on your shoulders, with elbows pointed forward. Step to the side with one foot until the thigh is almost parallel to the floor. The trailing leg will be slightly bent, with toes pointing straight ahead.